Electricity-Triggered Simultaneous Cesium and Bromide Ion Exchange of BiOBr in an Electrochemically Switched Ion Exchange Process

As an electrochemical material, BiOBr can exchange not only anions but also cations. Although many efforts have been made to study the exchange ability of BiOBr for a single anion or cation, few have been done to research the simultaneous exchanging properties of BiOBr for both anions and cations. In this work, the changes of Cs+ and Br– concentrations were monitored simultaneously in an electrochemically switched ion exchange (ESIX) process where the BiOBr film with mixed ion exchange ability was used as the working electrode. The experimental results reveal that BiOBr is dominated by the capture of Cs+ at a lower potential (−0.5 V) and release of Br– at a higher potential (−2.0 V). Moreover, density functional theory calculations indicate that the uptake of Cs+ is closely related to the release of Br– and the reduction of Bi3+ to Bi0. Here, the potential-dependent property of BiOBr is expected to expand its application in water treatment.